This proposal concerns mitotic spindle function in lysed mammalian tissue culture cells. Cells lysed early in anaphase into a mixture containing polyethylene glycol and nonionic detergents will continue to move chromosomes towards the spindle poles and display spindle elongation. This process requires ATP. The cells are permeable to dyes, ions and some proteins. This system is being used to characterize the nucleotide, divalent cation, ionic requirements for chromosome movement. The effects on chromosome movement of adding relevant proteins such as tubulin, dynein, actin and antibodies to various contractile proteins to the lysis medium are also being studied.